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Abstract:

This invention relates to compounds useful as ionic liquids that are
based on an N-substituted pyrrolidinone and incorporate a pendant
ammonium cation that is spaced from the pyrrolidone ring by a variable
length linker.

Claims:

1. A compound represented by the structure of the following Formula 1:
##STR00014## wherein (a) Z is --(CH2)n--, wherein n is an
integer from 2 to 12; (b) R2 are R3 are each independently H or
a C1 to C6 straight-chain or branched alkyl group; (c) R4
is --[(CH2)p--X]q--(CH2)r--Y--R6 wherein X
and Y are each independently O or NR6, r and p are each
independently an integer from 1 to 4, q is an integer from 0 to 8, and
R6 is H or a C1 to C6 straight-chain or branched alkyl
group; and (d) A.sup.- is an anion selected from the group consisting of
levulinate, [BF4].sup.-, [PF6].sup.-, [SbF6].sup.-,
[CH3CO2].sup.-, [HSO4].sup.-, [CF3SO3].sup.-,
[HCF2CF2SO3].sup.-, [CF3HFCCF2SO3].sup.-,
[CF3--O--CFHCF2SO3].sup.-,
[CF3CF2OCFHCF2SO3].sup.-,
[CF3CF2CF2OCFHCF2SO3].sup.-,
[HCClFCF2SO3].sup.-, [(CF3SO2)2N].sup.-,
[AlCl4].sup.-, [CF3CO2].sup.-, [NO3].sup.-,
[SO4]2-, Cl.sup.-, Br.sup.-, I.sup.-, and F.sup.-.

2. A compound according to claim 1 wherein Z is --(CH2)n--,
wherein n is an integer from 2 to 6.

3. A compound according to claim 1 wherein n is 2.

4. A compound according to claim 1 wherein q is 0 to 4.

5. A compound according to claim 1 wherein q is 0.

6. A compound according to claim 1 wherein r and p are 2 to 4.

7. A compound according to claim 1 wherein r and p are 2.

8. A compound according to claim 1 wherein R6 is H.

9. A compound according to claim 1 wherein R2 and R3 taken
independently are H, --CH3, --CH2CH3, and
--CH2CH2CH.sub.3.

10. A compound according to claim 1 wherein R2 and R3 are
--CH.sub.3.

11. A compound according to claim 1 wherein R4 is
--(CH2)2--O--(C2H5),
--(CH2)2----(CH3), or --(CH2)2--OH.

12. A compound according to claim 1 wherein A.sup.- is levulinate,
[CF3HFCCF2SO3].sup.-, or
[(CF3SO2)2N].sup.-.

13. A compound according to claim 1 wherein X and Y are O.

14. A compound according to claim 1 wherein X and Y are NR.sup.6.

15. A compound according to claim 1 wherein X is O and Y is NR.sup.6.

16. A compound according to claim 1 wherein X is NR6 and Y is O.

Description:

[0001] This application is a continuation-in-part of, and claims the
benefit of, U.S. application Ser. No. 12/328,078, filed Dec. 4, 2008,
which is by this reference incorporated in its entirety as a part hereof
for all purposes.

TECHNICAL FIELD

[0002] This invention relates to N-substituted pyrrolidonium compounds
that are useful as ionic liquids.

BACKGROUND

[0003] Ionic liquids are liquids composed of ions that are fluid at or
below about 100° C. Ionic liquids exhibit negligible vapor
pressure, and with increasing regulatory pressure to limit the use of
traditional industrial solvents due to environmental considerations such
as volatile emissions and aquifer and drinking water contamination, much
research has been devoted to designing ionic liquids that could function
as replacements for conventional solvents.

[0004] Ionic liquids typically consist of a salt of an organic cation such
as the N-alkylpyridinium, 1,3-dialkylimidazolium, tetraalkylammonium,
tetraalkylphosphonium or trialkylsulfonium cation. U.S. Pat. No.
7,157,588 describes, for example, ionic liquids based on N-substituted
pyrrolidones, which have a pendant ammonium cation that is spaced from
the pyrrolidone ring by a variable length linker. A need remains,
however, for other ionic liquids that may be designed for use in selected
applications, particularly those that may be prepared at least in part
from renewable resources.

SUMMARY

[0005] This invention provides a compound represented by the structure of
the following Formula 1:

##STR00001##

wherein

[0006] (a) Z is --(CH2)n--, wherein n is an integer from 2 to
12;

[0007] (b) R2 are R3 are each independently H or a C1 to
C6 straight-chain or branched alkyl group;

[0008] (c) R4 is
--[(CH2)p--X]q--(CH2)r--Y--R6 wherein X and
Y are each independently O, N or NR6, r and p are each independently
an integer from 1 to 4, q is an integer from 0 to 8, and each R6 is
independently H or a C1 to C6 straight-chain or branched alkyl
group; and

[0010] This invention relates to compounds that are derived, in part, from
N-substituted pyrrolidones. These compounds include an anion, and a
cation in which there is a pendant ammonium cation spaced from a
pyrrolidone ring by a variable length linker. This linker is denominated
Z in the description of Formula I as set forth herein. These compounds
are useful as ionic liquids, and can be used for example as a solvent, as
a catalyst for various kinds of reactions (such as an alkylation
reaction), and as an absorbent for various gases (such as CO2).
These compounds also have the advantage that the cationic portion, and
some of the associated anions, may be readily prepared from levulinic
acid, or levulinic acid derivatives, which may be obtained from the
hydrolysis of inexpensive renewable biomass feedstocks.

[0011] In the description of the compositions hereof, the following
definitional structure is provided for certain terminology as employed
variously in the specification:

[0012] An "alkyl" group is a monovalent (i.e. having a valence of one)
group having the general Formula CnH2n+1.

[0013] "Biomass" refers to any cellulosic or lignocellulosic material, and
includes materials containing cellulose, and optionally further includes
hemicellulose, lignin, starch, oligosaccharides and/or monosaccharides.
Biomass may also include additional components such as proteins and/or
lipids. Biomass suitable for use herein may be derived from a single
source, or may be a mixture derived from more than one source. Such
sources include without limitation bioenergy crops, agricultural
residues, municipal solid waste, industrial solid waste, sludge from
paper manufacture, yard waste, wood and forestry waste. Examples of
biomass include without limitation corn grain, corn cobs, crop residues
such as corn husks, corn stover, grasses, wheat, wheat straw, hay, rice
straw, switchgrass, waste paper, sugar cane bagasse, sorghum, soy,
residue from the milling of grain, trees, branches, roots, leaves, wood
chips, sawdust, shrubs and bushes, vegetables, fruits, flowers and animal
manure.

[0014] A "catalyst" is a substance that affects the rate of a reaction but
not the reaction equilibrium, and emerges from the reaction chemically
unchanged.

[0015] "Conversion" refers to the weight percent of a particular reactant
that is converted in a reaction to product.

[0016] A "hydrocarbyl" group is a monovalent group containing only carbon
and hydrogen.

[0017] An "ionic liquid" is an organic salts that is fluid at or below
about 100° C.

[0018] A "levulinate" ion is an anion represented by the structure of the
following formula:

##STR00002##

[0019] A "metal catalyst" is a catalyst that includes at least one metal,
at least one Raney® metal, compounds thereof or combinations thereof.
A supported metal catalyst is a supported catalyst in which the catalyst
agent is a metal.

[0020] A "metal promoter" is a metallic compound that is added to a
catalyst to enhance the physical or chemical function thereof in a
reaction. A metal promoter can also be added to retard undesirable side
reactions and/or affect the rate of the reaction.

[0021] A "promoter" is an element of the periodic table that is added to a
catalyst to enhance the physical or chemical function thereof in a
reaction. A promoter can also be added to retard undesirable side
reactions and/or affect the rate of the reaction.

[0022] "Pyrrolidinone" is used synonymously with the term "pyrrolidone";
"pyrrolidin-2-one" is used synonymously with the term "2-pyrrolidone".

[0023] "Selectivity" refers to the weight percent of a particular reaction
product in the total weight of the product of a reaction (including the
weight of unreacted reactants).

[0024] This invention provides compounds represented by the structure of
the following Formula 1:

##STR00003##

wherein (a) Z is --(CH2)n--, wherein n is an integer from 2 to
12; (b) R2 are R3 are each independently H or a C1 to
C6 straight-chain or branched alkyl group; (c) R4 is
--[(CH2)p--X]q--(CH2)r--Y--R6 wherein X and
Y are each independently O, N or NR6, r and p are each independently
an integer from 1 to 4, q is an integer from 0 to 8, and each R6 is
independently H or a C1 to C6 straight-chain or branched alkyl
group; and (d) A.sup.- is an anion selected from the group consisting of
levulinate, [BF4].sup.-, [PF6].sup.-, [SbF6].sup.-,
[CH3CO2].sup.-, [HSO4].sup.-, [CF3SO3].sup.-,
[HCF2CF2SO3].sup.-, [CF3HFCCF2SO3].sup.-,
[CF3--O--CFHCF2SO3].sup.-,
[CF3CF2OCFHCF2SO3].sup.-,
[CF3CF2CF2OCFHCF2SO3].sup.-,
[HCClFCF2SO3].sup.-, [(CF3SO2)2N].sup.-,
[AlCl4].sup.-, [CF3CO2].sup.-, [NO3].sup.-,
[SO4]2-, Cl.sup.-, Br.sup.-, I.sup.-, and F.sup.-.

[0025] In various embodiments, n in Z may be an integer from 2 to 6, and
is frequently 2. In other embodiments, R2 and R3 may each
independently be H, --CH3, --CH2CH3 or
--CH2CH2CH3, and frequently R2 is --CH3 and
R3 is --CH2CH2CH3. In other embodiments, r and p are
2 to 4, more typically 2. In another embodiment q is 0 to 4, more
typically 0. In other embodiments, X and Y are both O, or X and Y are
both N or NR6, more typically Y is O and/or X is N or NR6; or X
is O and/or Y is N or NR6. In other embodiments, R6 is H,
R2 and R3 are --CH3, R4 is
--(CH2)2--O--(C2H5),
--(CH2)2--O--(CH3) or --(CH2)2--OH, and Ais levulinate, [CF3HFCCF2SO3].sup.- or
[(CF3SO2)2N].sup.-.

[0026] A compound hereof may be synthesized from a pyrrolidin-2-one as
represented by the structure of the following Formula 2, wherein Z,
R2 and R3 are as defined above.

##STR00004##

Synthesis of an N-hydrocarbyl pyrrolidin-2-one

[0027] The pyrrolidin-2-one may be synthesized by contacting levulinic
acid, or an ester thereof, with a diamine of the Formula
R2R3N--Z--NH2 in the presence of hydrogen gas and a
catalyst according to Reaction (I):

##STR00005##

wherein Z, R2 and R3 are as defined above, and R5 is H,
--CH3, --CH2CH3, or a C3 to C8 straight-chain or
branched alkyl group. In another embodiment, the pyrrolidin-2-one may be
synthesized by contacting a salt of levulinic acid, such as ammonium
levulinate, with a diamine of the Formula R2R3N--Z--NH2 in
the presence of hydrogen gas and a catalyst. In various embodiments, in a
diamine suitable for use herein, Z may be --(CH2)n-- wherein n
is an integer from 2 to 12, and R2 and R3 may each
independently be H, --CH3, --CH2CH3 or a C3 to
C6 straight-chain or branched alkyl group.

[0028] The pyrrolidin-2-one formed in Reaction (I) can be synthesized
according to methods and conditions as taught in or adapted from U.S.
Pat. Nos. 6,818,593 or 6,900,337, each of which is by this reference
incorporated in its entirety as a part hereof for all purposes. For the
synthesis of a pyrrolidin-2-one according to Reaction (I), a molar ratio
of diamine to levulinic acid, or a salt or ester thereof, at the start of
the reaction may be about 0.01/1 to about 100/1, or about 0.3/1 to about
5/1. The temperature range for this reductive amination reaction may be
from about 25° C. to about 300° C., or about 75° C.
to about 200° C. The pressure may be in the range of from about
0.3 MPa to about 20.0 MPa, or from about 1.3 MPa to about 7.6 MPa. The
reaction may be performed in a non-reacting solvent medium such as water
or an alcohol, ether or pyrrolidone. Alternatively, an excess of diamine
can also act as a reaction medium.

[0029] The principal component of a catalyst suitable for use in Reaction
(I) may be selected from metals from the group consisting of palladium,
ruthenium, rhenium, rhodium, iridium, platinum, nickel, cobalt, copper,
iron, osmium; compounds thereof; and combinations thereof. A chemical
promoter may augment the activity of the catalyst. The promoter may be
incorporated into the catalyst during any step in the chemical processing
of the catalyst constituent. Suitable promoters for this process include
metals selected from tin, zinc, copper, gold, silver, and combinations
thereof. The preferred metal promoter is tin. Other promoters that can be
used are elements selected from Group 1 and Group 2 of the Periodic
Table.

[0030] The catalyst may be supported or unsupported. A supported catalyst
is one in which the active catalyst agent is deposited on a support
material by a number of methods such as spraying, soaking or physical
mixing, followed by drying, calcination and if necessary, activation
through methods such as reduction or oxidation. Materials frequently used
as a support are porous solids with high total surface areas (external
and internal) that can provide high concentrations of active sites per
unit weight of catalyst. A catalyst support may enhance the function of
the catalyst agent.

[0031] The catalyst support useful herein can be any solid, inert
substance including without limitation oxides such as silica, alumina and
titania; barium sulfate; calcium carbonate; and carbons. The catalyst
support can be in the form of powder, granules, pellets, or the like. A
preferred support material is selected from the group consisting of
carbon, alumina, silica, silica-alumina, silica-titania, titania,
titania-alumina, barium sulfate, calcium carbonate, strontium carbonate,
compounds thereof and combinations thereof. Supported metal catalysts can
also have supporting materials made from one or more compounds. More
preferred supports are carbon, titania and alumina. Further preferred
supports are carbons with a surface area greater than 100 m2/g. A
further preferred support is carbon with a surface area greater than 200
m2/g. Preferably, the carbon has an ash content that is less than 5%
by weight of the catalyst support, where the ash content is the inorganic
residue (expressed as a percentage of the original weight of the carbon)
which remains after incineration of the carbon.

[0032] The preferred content of a metal catalyst in a supported catalyst
is from about 0.1 wt % to about 20 wt % of the supported catalyst based
on metal catalyst weight plus the support weight. A more preferred metal
catalyst content range is from about 1 wt % to about 10 wt % of the
supported catalyst. Combinations of metal catalyst and support may
include any one of the metals referred to herein with any of the supports
referred to herein. Preferred combinations of metal catalyst and support
include palladium on carbon, palladium on calcium carbonate, palladium on
barium sulfate, palladium on alumina, palladium on titania, platinum on
carbon, platinum on alumina, platinum on silica, iridium on silica,
iridium on carbon, iridium on alumina, rhodium on carbon, rhodium on
silica, rhodium on alumina, nickel on carbon, nickel on alumina, nickel
on silica, rhenium on carbon, rhenium on silica, rhenium on alumina,
ruthenium on carbon, ruthenium on alumina and ruthenium on silica.
Further preferred combinations of metal catalyst and support include
palladium on carbon, palladium on alumina, palladium on titania, platinum
on carbon, platinum on alumina, rhodium on carbon, rhodium on alumina,
ruthenium on carbon and ruthenium on alumina.

[0033] A catalyst that is not supported on a catalyst support material is
an unsupported catalyst. An unsupported catalyst may be platinum black or
a Raney® (W.R. Grace & Co., Columbia Md.) catalyst. Raney®
catalysts have a high surface area as a result of preparation by the
selective leaching of an alloy containing the active metal(s) and a
leachable metal (usually aluminum). Raney® catalysts have high
activity due to the higher specific area and allow the use of lower
temperatures in hydrogenation reactions. The active metals of Raney®
catalysts include nickel, copper, cobalt, iron, rhodium, ruthenium,
rhenium, osmium, iridium, platinum, palladium; compounds thereof; and
combinations thereof. Promoter metals may also be added to the base
Raney® metals to affect selectivity and/or activity of the Raney®
catalyst. Promoter metals for Raney® catalysts may be selected from
transition metals from Groups IIIA through VIIIA, IB and IIB of the
Periodic Table of the Elements. Examples of promoter metals include
chromium, molybdenum, platinum, rhodium, ruthenium, osmium and palladium,
typically at about 2% by weight of the weight of the total metal.

[0034] Levulinic acid for use herein may be obtained from biomass. For the
conversion of biomass to levulinic acid, biomass may be contacted with
water and an acid catalyst in a train of one or more reactors, preferably
under pressure at elevated temperature. This basic process is described,
for example, in U.S. Pat. Nos. 5,608,105, 5,859,263, 6,054,611 and
7,153,996, each of which is by this reference incorporated in its
entirety as a part hereof for all purposes. Generally, cellulose in the
biomass is converted to levulinic acid and formate in one or more
reactors. Levulinic acid produced from biomass may also be converted to
levulinic acid esters for example as described in U.S. Pat. No. 7,153,996
through the reaction of levulinic acid with olefins.

[0035] Suitable diamines for use in Reaction (I) may, for example, be
obtained commercially from suppliers such as Huntsman (Houston Tex.) or
BASF (Mount Olive N.J.), or may be synthesized by methods such as those
discussed in Eller and Henkes, Diamines and Polyamines [in Chapter 8 of
Ullmanns Encyclopedia of Industrial Chemistry (2002), Wiley-VCH Verlag
GmbH & Co.], or Chapter 22 in Experimental Methods in Organic Chemistry,
3rd Edition [Moore, Dalrymple and Rodig (Eds.), (1982) Saunders
College Publishing, NY].

[0036] The formation of a pyrrolidin-2-one may be carried out in batch,
sequential batch (i.e. a series of batch reactors) or in continuous mode
in equipment such as that discussed in Fogler, Elementary Chemical
Reaction Engineering, 2nd Edition [(1992), Prentice-Hall, Inc.,
N.J., USA]. A pyrrolidin-2-one synthesized according to Reaction (I) may
be recovered, for example, by distillation, or by filtration to remove
solid acid catalyst particles, if present.

Conversion of the N-hydrocarbyl pyrrolidin-2-one

[0037] A compound hereof may be synthesized by quaternizing the non-ring
nitrogen of the pyrrolidin-2-one to obtain a quaternary ammonium compound
as represented by the structure of the following Formula 3:

##STR00006##

wherein Z, R2, R3 and R4 are each as defined above, and
A'.sup.- is selected from the group consisting of Cl.sup.-, Br.sup.- and
I.sup.-.

[0038] To form a quaternary ammonium compound as described above, the
pyrrolidin-2-one is contacted with an alkylating halide having the
Formula R4-A wherein R4 is as described above, and A'.sup.- is
selected from the group consisting of Cl.sup.-, Br.sup.- and I.sup.-.
Compounds of the formula R4-A' can be obtained commercially, or can
be prepared by methods such as those discussed in U.S. Pat. Nos.
2,913,496, 4,820,672 or 6,136,586; Cardoso et al, J. Polymer Sci., Part
B: Polymer Physics (1997), 35(3), 479-488; or Lermit et al, J. of the
Chem. Soc. (1947), 530-3.

[0039] The quaternization reaction may be carried out in an inert solvent
such as acetonitrile, acetone or dichloromethane. The quaternization may
be accomplished by refluxing of the reactants, optionally under an inert
atmosphere. When the reactants are hygroscopic, it is preferable to carry
out the quaternization reaction, and/or the anion exchange reaction
described below, under conditions that exclude water and air. The
alkylating halide is present in slight excess (e.g. about 5 wt % excess)
at the start of the reaction. The reaction may be carried out at a
temperature in the range of from about 10° C. to about 100°
C.; or in the range of from about 30° C. to about 90° C.;
or in the range of from about 60° C. to about 90° C. The
time for the reaction is generally from about 1 minute to about 72 hours,
or about 30 minutes to about 24 hours. Methods for performing
quaternization reactions suitable for use for such purpose are further
discussed in sources such as Organic Chemistry [Morrison and Boyd (ed.)
3rd Edition (1973); Allyn and Bacon, Inc., Boston; Chapter 23.5,
pages 752-753].

Anion Exchange

[0040] The quaternary ammonium compound thus formed is next contacted with
M+A.sup.-, wherein M is selected from the group consisting of H, Li,
K, Na, Ag, Mg, Ca, Ce, Ba, Rb and Sr, and A.sup.- is an anion selected
from the group consisting of [BF4].sup.-, [PF6].sup.-,
[SbF6].sup.-, [CH3CO2].sup.-, [HSO4].sup.-,
[NO3].sup.-, [CF3SO3].sup.-,
[HCF2CF2SO3].sup.-,
[CF3--O--CFHCF2SO3].sup.-,
[CF3CF2OCFHCF2SO3].sup.-,
[CF3CF2CF2OCFHCF2SO3].sup.-,
[CF3HFCCF2SO3].sup.-, [HCClFCF2SO3].sup.-,
[(CF3SO2)2N].sup.-, [AlCl4].sup.-,
[CF3CO2].sup.-, [NO3].sup.-, [SO4]2-, Cl.sup.-,
Br.sup.-, I.sup.- F.sup.- and levulinate, to form a compound hereof
according to the choice of anion desired. Prior to the exchange reaction,
excess alkylating agent may be removed, for example, by evaporation. In
addition, the quaternary ammonium compound may be washed with a solvent
and dried prior to anion exchange.

[0041] The anion exchange reaction may be carried out by mixing the
quaternary ammonium compound with M+A.sup.-, optionally under an
inert atmosphere. The anion exchange reaction may be carried out at a
temperature in the range of from about -20 C. to about 100° C. for
a time of about 1 second to about 72 hours. Solvents useful in the
reaction should be inert to the reactants and products, and include, for
example, methanol, ethanol, acetone and/or acetonitrile. Choice of the
solvent or mixture thereof will facilitate separation of the compound
containing the desired anion from the remainder of the reaction mixture.
Additional techniques that may enhance the anion exchange reaction
include as ultrasonication as discussed in WO 03/048078.

[0042] Fluoroalkyl sulfonate anions suitable for used in the anion
exchange reaction may be synthesized from perfluorinated terminal olefins
or perfluorinated vinyl ethers generally according to the methods
discussed in Koshar et al [J. Am. Chem. Soc. (1953) 75:4595-4596], U.S.
Ser. No. 06/276,670 and U.S. Ser. No. 06/276,671. In one embodiment,
sulfite and bisulfite are used as a buffer in place of bisulfite and
borax, and in another embodiment, the reaction is carried out in the
absence of a radical initiator. The product of the anion exchange
reaction may be recovered by a technique such as evaporation of the
reaction solvent under reduced pressure, decantation and/or filtration to
remove precipitated salts.

[0043] 1,1,2,2-Tetrafluoroethanesulfonate,
1,1,2,3,3,3-hexafluoropropanesulfonate,
1,1,2-trifluoro-2-(trifluoromethoxy)ethanesulfonate, and
1,1,2-trifluoro-2-(pentafluoroethoxy)ethanesulfonate may be synthesized
according to a modifications of Koshar in which

[0044] a mixture of sulfite and bisulfite is used as the buffer, and
freeze drying or spray drying isolates the crude
1,1,2,2-tetrafluoroethanesulfonate and
1,1,2,3,3,3-hexafluoropropanesulfonate products from the aqueous reaction
mixture,

[0045] acetone is used to extract the crude
1,1,2,2-tetrafluoroethanesulfonate and
1,1,2,3,3,3-hexafluoropropanesulfonate salts; and

[0046] 1,1,2-trifluoro-2-(trifluoromethoxy)ethanesulfonate and
1,1,2-trifluoro-2-(pentafluoroethoxy)ethanesulfonate are crystallized
from the reaction mixture by cooling.

[0047] Each of the formulae shown herein describes each and all of the
separate, individual compounds that can be assembled in that formula by
(1) selection from within the prescribed range for one of the variable
radicals, substituents or numerical coefficents while all of the other
variable radicals, substituents or numerical coefficents are held
constant, and (2) performing in turn the same selection from within the
prescribed range for each of the other variable radicals, substituents or
numerical coefficents with the others being held constant. In addition to
a selection made within the prescribed range for any of the variable
radicals, substituents or numerical coefficents of only one of the
members of the group described by the range, a plurality of compounds may
be described by selecting more than one but less than all of the members
of the whole group of radicals, substituents or numerical coefficents.
When the selection made within the prescribed range for any of the
variable radicals, substituents or numerical coefficents is a subgroup
containing (i) only one of the members of the whole group described by
the range, or (ii) more than one but less than all of the members of the
whole group, the selected member(s) are selected by omitting those
member(s) of the whole group that are not selected to form the subgroup.
The compound, or plurality of compounds, may in such event be
characterized by a definition of one or more of the variable radicals,
substituents or numerical coefficents that refers to the whole group of
the prescribed range for that variable but where the member(s) omitted to
form the subgroup are absent from the whole group.

[0048] In various embodiments of this invention, an ionic liquid may be
formed by selecting any of the individual cations described or disclosed
herein, and by selecting to pair therewith any of the individual anions
described or disclosed herein, and the ionic liquid(s) thus formed may be
used for any of the purposes disclosed herein such as carbon dioxide
absorption. Correspondingly, in yet other embodiments, a subgroup of
ionic liquids may be formed by selecting a subgroup of any size of
cations, taken from the total group of cations described and disclosed
herein in all the various different combinations of the individual
members of that total group, and pairing therewith a subgroup of any size
of anions, taken from the total group of anions described and disclosed
herein in all the various different combinations of the individual
members of that total group. In forming an ionic liquid, or a subgroup of
ionic liquids, by making selections as aforesaid, the ionic liquid or
subgroup will be formed in the absence of the members of the group of
cations and/or anions that are omitted from the total group thereof to
make the selection, and, if desirable, the selection may thus be made in
terms of the members of the total group that are omitted from use rather
than the members of the group that are included for use.

[0049] The compounds hereof are useful as ionic liquids, and are in
general fluid at or below a temperatures of about 100° C. The
physical and chemical properties of an ionic liquid are influenced by the
choice of cation. For example, increasing the chain length of one or more
of the alkyl chains of the cation will affect properties such as the
melting point, hydrophilicity/lipophilicity, density, viscosity, and
solvation strength of the ionic liquid. Effects of the choice of cation
and anion on the physical and chemical properties of an ionic liquid are
further discussed in sources such as Wasserscheid and Keim [Angew. Chem.
Int. Ed., 39, 3772-3789 (2000)] and Sheldon [Chem. Commun., 2399-2407
(2001)]. The compounds hereof may be utilized in one-phase systems or
multiple-phase systems as a solvent, as a catalyst for various kinds of
reactions (such as an alkylation reaction), and as an absorbent for
various gases (such as CO2).

[0050] Other related N-substituted pyrrolidonium compounds, and methods
for using same for carbon dioxide absorption, are disclosed in the
concurrently-filed, commonly-assigned applications listed as follows by
attorney docket number and title, each of which is by this reference
incorporated in its entirety as a part hereof for all purposes, to-wit:
[0051] CL4180 US NA (N-Substituted Pyrrolidonium Ionic Liquids), now U.S.
application Ser. No. 12/______; [0052] CL4349 US PRV (N-Substituted
Pyrrolidonium Ionic Liquids with Expanded Linker), now U.S. Provisional
Application No. 61/______; and [0053] CL4398 US PRV (Carbon Dioxide
Removal and Ionic Liquid Compounds Useful Therein), now U.S. Provisional
Application No. 61/______.

EXAMPLES

[0054] Compounds provided by this invention, and the advantageous
attributes and effects thereof, may be seen in a series of examples as
described below. The embodiments of this invention on which the examples
are based are representative only, and the selection of those embodiments
to illustrate the invention does not indicate that materials, components
and reactants, and/or conditions, protocols and regimes, not described in
these examples are not suitable for practicing this invention, or that
subject matter not described in these examples is excluded from the scope
of the appended claims and equivalents thereof.

[0060] Example 1 illustrates a method for the preparation of the
1-(2-(dimethylamino)ethyl)-5-methylpyrrolidin-2-one (MeDMAP) intermediate
used in the subsequent preparation of various exemplary ionic liquids.
Examples 2-6 describe the preparation of several exemplary ionic liquids
representative of a class of compounds that are based on this MeDMAP
intermediate.

[0061] 1-(2-(dimethylamino)ethyl)-5-methylpyrrolidin-2-one (MeDMAP),
C9H18N2O, with a molecular weight of 170.25 g mol-1
and structure as shown in Formula 4:

##STR00007##

was prepared as described below via the cyclic reductive amination of
ethyl levulinate with N,N-dimethylethylenediamine (and as described in
U.S. Pat. No. 7,157,588):

[0062] To a 600-mL Hastelloy® C-276 autoclave reactor (Parr Model 2302
HC) equipped with a gas entrainment turbine impellor and electrical
heating mantle was added 150.0 g (1.04 mol) ethyl levulinate, 192.6 g
(2.18 mol) N,N-dimethylethylenediamine, and 7.5 g ESCAT® 142 5% Pd/C
catalyst. The reactor was purged first with nitrogen and then hydrogen,
and then pressurized with 50 psig (0.4 MPa) hydrogen and stirred at 600
rpm while heating the reaction mixture to 150° C. On reaching this
reaction temperature, the reactor was further pressurized to 1000 psig
(7.0 MPa) with hydrogen and maintained at this pressure by adding
additional hydrogen as required for the duration of the reaction.

[0063] After 6 hours at these conditions, the reactor was cooled and
vented, and the liquid reaction mixture was recovered for product
isolation. The crude mixture was filtered through a glass frit via
aspirator vacuum to remove the catalyst, followed by removal of byproduct
ethanol and unreacted N,N-dimethylethylenediamine in vacuo. The remaining
contents were fractionally distilled with a 20-cm Vigreaux column under
high vacuum (˜0.05 mmHg) to give 136.5 g water-white product at
85° C. in 77% isolated yield. Product purity was >99% as
determined by GC/MS (HP-6890 equipped with MSD).

[0064] 1-(N,N,N-dimethyl(ethylethoxy)aminoethyl)-5-methyl-pyrrolidin-2-one
bis(trifluoromethane)sulfonamide ([MeDMEEAP] [TF2N]),
C15H27N3O6 F6S2, with a molecular weight of
523.51 g mol-1 and structure as shown in Formula 5, was prepared as
follows:

##STR00008##

[0065] 1-(2-(dimethylamino)ethyl)-5-methylpyrrolidin-2-one (MeDMAP),
C9H18N2O, with a molecular weight of 170.25 g mol-1
and a purity of >99% by GC/MS, was used as prepared in Example 1. To a
two-neck 100-mL round bottom flask equipped with a nitrogen-purged reflux
condenser was added 24.27 g (0.143 moles) MeDMAP, 30.40 g (0.280 moles)
2-chloroethyl ethyl ether, and 17.81 g acetonitrile as reaction solvent.
The condenser was cooled by a recirculating bath filled with a 50 wt %
mixture of water and propylene glycol maintained at approximately
16° C. The reaction mixture was heated to 85° C. under
reflux and nitrogen purge with a temperature-controlled oil bath. This
reaction temperature was maintained for 120 hrs, at which time the
conversion of the MeDMAP was about 94.4% by 1H NMR spectroscopy.

[0066] The reaction mixture was then thermally quenched and extracted with
multiple diethyl ether and ethyl acetate washes to remove starting
materials and to purify the intermediate product. The solvents were
removed in vacuo with a rotary evaporator, and the intermediate product
was then dried under high vacuum (approximately 10-6 torr) using a
turbomolecular pump and heating the material to about 70-80° C.
overnight. The resulting intermediate product of this reaction,
1-(N,N,N-dimethyl(ethylethoxy)aminoethyl)-5-methyl-pyrrolidin-2-one
chloride ([MeDMEEAP] [Cl]), C13H27N2O2Cl, with a
molecular weight of 278.82 g mol-1, was determined to have a final
purity of about 95.1% by 1H NMR spectroscopy.

[0067] In a 500-mL round bottom flask, 11.50 g (0.0413 mol) of this
[MeDMEEAP] [Cl] intermediate was dissolved in approximately 150 mL of
purified water, chilled in an ice bath, and then mixed with 12.81 g
(0.0456 mol) bis(trifluoromethane)sulfonimide dissolved in approximately
150 mL water. After stirring the reaction solution overnight at room
temperature, the resulting IL was purified by extracting the resulting
hydrochloric acid and the excess bis(trifluoromethane)sulfonamide with
multiple water washes of about 15 mL each while keeping the IL product
partitioned in an organic phase with dichloromethane. Water was removed
from the filtrate in vacuo with a rotary evaporator, then the product was
dried under high vacuum (approximately 10-5 torr) using a
turbomolecular pump and heating the material to about 70° C.
overnight. The resulting [MeDMEEAP] [Tf2N] product purity was
estimated to be about 95% by 1H NMR spectroscopy.

[0068] 1-(N,N,N-dimethyl(ethylethoxy)aminoethyl)-5-methyl-pyrrolidin-2-one
hexafluoropropanesulfonate ([MeDMEEAP] [HFPS]),
C15H26N2O5F6S, with a molecular weight of 460.43
g mol-1 and structure as shown in Formula 6, was prepared as
follows:

##STR00009##

[0069] 1-(N,N,N-dimethyl(ethylethoxy)aminoethyl)-5-methyl-pyrrolidin-2-one
chloride ([MeDMEEAP] [Cl]), C13H27N2O2Cl, with a
molecular weight of 278.82 g mol-1 and final purity of about 95.1%
by 1H NMR spectroscopy, was used as prepared in Example 5. In a
500-mL round bottom flask, 11.28 g (0.0405 mol) of this 95% [MeDMEEAP]
[Cl] intermediate was dissolved in approximately 100 mL of acetone, and
then 10.51 g (0.0389 mol) potassium hexafluoropropanesulfonate dissolved
in approximately 50 mL of acetone was slowly added. After stirring the
reaction solution overnight at room temperature, the IL product was
filtered through a fritted funnel to remove the resulting potassium
chloride crystals. The filtrate was allowed to set for about a week, and
additional potassium chloride crystals formed and were removed by
filtration through a fritted funnel. The solvent was removed in vacuo
with a rotary evaporator, and then the product was dried under high
vacuum (approximately 10-5 torr) using a turbomolecular pump and
heating the material to about 70° C. overnight. The final purity
of the resulting [MeDMEEAP] [HFPS] product was approximately 98% by
1H NMR spectroscopy.

[0070] 1-(N,N,N-dimethyl(methylethoxy)aminoethyl)-5-methylpyrrolidin-2-one
bis(trifluoromethane)sulfonamide ([MeDMMEAP] [TF2N]),
C14H25N3O6F6S2, with a molecular weight of
509.49 g mol-1 and structure as shown in Formula 7, was prepared as
follows:

##STR00010##

[0071] 1-(2-(dimethylamino)ethyl)-5-methylpyrrolidin-2-one (MeDMAP),
C9H18N2O, with a molecular weight of 170.25 g mol-1
and a purity of >99% by GC/MS, was used as prepared in Example 1. To a
two-neck 100-mL round bottom flask equipped with a nitrogen-purged reflux
condenser was added 20.88 g (0.123 moles) MeDMAP, 23.93 g (0.253 moles)
2-chloroethyl methyl ether, and 25.03 g acetonitrile as reaction solvent.
The condenser was cooled by a recirculating bath filled with a 50 wt %
mixture of water and propylene glycol maintained at approximately
16° C. The reaction mixture was heated to 85° C. under
reflux and nitrogen purge with a temperature-controlled oil bath. This
reaction temperature was maintained for 116 hrs, at which time the
conversion of the MeDMAP was about 95.5% by 1H NMR spectroscopy.

[0072] The reaction mixture was thermally quenched at about 120 hrs
reaction time. The intermediate product of this reaction,
1-(N,N,N-dimethyl(methylethoxy)aminoethyl)-5-methylpyrrolidin-2-one
chloride ([MeDMMEAP] [Cl]), C12H25N2O2Cl, with a
molecular weight of 264.79 g mol-1, was then extracted with multiple
diethyl ether extractions (approximately 220 mL in 30-40 mL increments)
to remove starting materials. The reaction mixture was then dissolved in
dichloromethane and filtered through a column packed with acidic and
neutral alumina. The solvent was removed from the filtrate in vacuo with
a rotary evaporator, and the product was then dried under high vacuum
(approximately 10-6 torr) using a turbomolecular pump and heating
the material to about 70-80° C. overnight. The final purity of
this chloride salt intermediate was approximately 96.4% by H NMR
spectroscopy.

[0073] In a 500-mL round bottom flask, 13.07 g (0.0494 mol) of this
[MeDMMEAP] [Cl] intermediate was dissolved in approximately 150 mL of
purified water, chilled in an ice bath, and then mixed with 15.54 g
(0.0553 mol) bis(trifluoromethane)sulfonimide dissolved in approximately
150 mL water. After stirring the reaction solution overnight at room
temperature, the resulting IL was purified by extracting the resulting
hydrochloric acid and the excess bis(trifluoromethane)sulfonamide with
multiple water washes of about 15 mL each while keeping the IL product
partitioned in an organic phase with dichloromethane. Water was removed
from the filtrate in vacuo with a rotary evaporator, then the product was
dried under high vacuum (approximately 10-5 torr) using a
turbomolecular pump and heating the material to about 70° C.
overnight. The resulting [MeDMMEAP] [Tf2N] product purity was
estimated to be about 96% by 1H NMR spectroscopy.

[0074] 1-(N,N,N-dimethyl(methylethoxy)aminoethyl)-5-methylpyrrolidin-2-one
hexafluoropropanesulfonate ([MeDMMEAP] [HFPS]),
C15H26N2O5F6S, with a molecular weight of 460.43
g mol-1 and structure as shown in Formula 8, was prepared as
follows:

##STR00011##

[0075] 1-(N,N,N-dimethyl(methylethoxy)aminoethyl)-5-methylpyrrolidin-2-one
chloride ([MeDMMEAP] [Cl]), C12H25N2O2Cl, with a
molecular weight of 264.79 g mol-1 and a purity of about 96.4% by
1H NMR spectroscopy was used as prepared in Example 4.

[0076] In a 500-mL round bottom flask, 12.94 g (0.0489 mol) of this 96.4%
[MeDMMEAP] [Cl] intermediate was dissolved in approximately 100 mL of
acetone, and then 14.59 g (0.0540 mol) potassium
hexafluoropropanesulfonate was slowly added to this mixture. After
stirring the reaction solution overnight at room temperature, the IL
product was filtered through a fritted funnel containing Celite® to
remove the resulting potassium chloride crystals. The solvent was removed
in vacuo with a rotary evaporator, and then the [MeDMMEAP] [HFPS] product
was dissolved in dichloromethane and filtered through a column containing
basic and neutral alumina. Methanol and dichloromethane were used to
recover the product from the column. The solvent was removed in vacuo
with a rotary evaporator, and then the product was dried under high
vacuum (approximately 10-5 torr) using a turbomolecular pump and
heating the material to about 70° C. overnight. The final purity
of the resulting [MeDMMEAP] [HFPS] product was approximately 96% by
1H NMR spectroscopy.

[0077] 1-(N,N,N-dimethyl(hyrdoxyethyl)aminoethyl)-5-methylpyrrolidin-2-one
bis(trifluoromethane)sulfonamide ([MeDMHEAP] [TF2N]),
C13H23N3O6F6S2, with a molecular weight of
495.46 g mol-1 and structure as shown in Formula 9, was prepared as
follows:

##STR00012##

[0078] 1-(2-(dimethylamino)ethyl)-5-methylpyrrolidin-2-one (MeDMAP),
C9H18N2O, with a molecular weight of 170.25 g mol-1
and a purity of >99% by GC/MS, was used as prepared in Example 1.

[0079] To a two-neck 100-mL round bottom flask equipped with a
nitrogen-purged reflux condenser was added 16.97 g (0.0997 moles) MeDMAP,
15.92 g (0.198 moles) 2-chloroethanol, and 18.63 g acetonitrile as
reaction solvent. The condenser was cooled by a recirculating bath filled
with a 50 wt % mixture of water and propylene glycol maintained at
approximately 16° C. The reaction mixture was heated to 85°
C. under reflux and nitrogen purge with a temperature-controlled oil
bath. This reaction temperature was maintained for 100 hrs, and then the
reaction mixture was thermally quenched and dried under high vacuum
(approximately 10-5 torr) using a turbomolecular pump and heating
the material to about 70° C. overnight. The intermediate product
of this reaction,
1-(N,N,N-dimethyl(hyrdoxyethyl)aminoethyl)-5-methylpyrrolidin-2-one
chloride ([MeDMHEAP] [Cl]), C11H23N2O2Cl, with a
molecular weight of 250.77 g mol-1, was determined to have a final
purity of 95.6% by 1H NMR spectroscopy.

[0080] In a 500-mL round bottom flask, 13.75 g (0.0548 mol) of this
[MeDMMEAP] [Cl] intermediate was dissolved in approximately 150 mL of
purified water, chilled in an ice bath, and then mixed with 15.95 g
(0.0567 mol) bis(trifluoromethane)sulfonimide dissolved in approximately
150 mL water. After stirring the reaction solution overnight at room
temperature, the resulting IL was purified by extracting the resulting
hydrochloric acid and the excess bis(trifluoromethane)sulfonamide with
multiple water washes of about 15 ml each while keeping the IL product
partitioned in an organic phase with dichloromethane. Water was removed
from the filtrate in vacuo with a rotary evaporator, then the product was
dried under high vacuum (approximately 10-5 torr) using a
turbomolecular pump and heating the material to about 70° C.
overnight. The resulting [MeDMMEAP] [Tf2N] product purity was
estimated to be 97.8% by 1H NMR spectroscopy.

[0081] 1-(N,N,N-dimethyl(hyrdoxyethyl)aminoethyl)-5-methylpyrrolidin-2-one
levulinate ([MeDMHEAP] [Lev]), C16H30N2O5, with a
molecular weight of 330.42 g mol-1 and structure as shown in Formula
10, was prepared as follows:

##STR00013##

[0082] 1-(N,N,N-dimethyl(hyrdoxyethyl)aminoethyl)-5-methylpyrrolidin-2-one
chloride ([MeDMHEAP] [Cl]), C11H23N2O2Cl, with a
molecular weight of 250.77 g mol-1 and final purity of 95.6%, was
prepared as described in Example 5.

[0083] In a 500-mL Erlenmeyer flask, 12.550 (0.0500 mol) of this
[MeDMHEAP] [Cl] intermediate dissolved in approximately 150 mL of
purified water was combined with a slurry of 5.794 g (0.0250 mol)
silver(I) oxide and 6.433 g (0.0554 mol) levulinic acid in approximately
200 mL of purified water. After stirring overnight at room temperature,
the reaction mixture was filtered through a fritted funnel containing
Celite® to remove the silver chloride product and residual silver(I)
oxide. Water was removed from the filtrate in vacuo with a rotary
evaporator, and then the product was twice dissolved in methanol,
filtered through a fritted funnel containing Celite® to remove
residual silver chloride and silver(I) oxide, and then evaporated in
vacuo with a rotary evaporator to remove the methanol solvent. The
product was then dried under high vacuum (approximately 10-5 torr)
using a turbomolecular pump and heating the material to about 70°
C. for two days. The resulting [MeDMHEAP] [Lev] product was 98.9% purity
by 1H NMR spectroscopy.

[0084] Where a range of numerical values is recited or established herein,
the range includes the endpoints thereof and all the individual integers
and fractions within the range, and also includes each of the narrower
ranges therein formed by all the various possible combinations of those
endpoints and internal integers and fractions to form subgroups of the
larger group of values within the stated range to the same extent as if
each of those narrower ranges was explicitly recited. Where a range of
numerical values is stated herein as being greater than a stated value,
the range is nevertheless finite and is bounded on its upper end by a
value that is operable within the context of the invention as described
herein. Where a range of numerical values is stated herein as being less
than a stated value, the range is nevertheless bounded on its lower end
by a non-zero value.

[0085] In this specification, unless explicitly stated otherwise or
indicated to the contrary by the context of usage, amounts, sizes,
ranges, formulations, parameters, and other quantities and
characteristics recited herein, particularly when modified by the term
"about", may but need not be exact, and may also be approximate and/or
larger or smaller (as desired) than stated, reflecting tolerances,
conversion factors, rounding off, measurement error and the like, as well
as the inclusion within a stated value of those values outside it that
have, within the context of this invention, functional and/or operable
equivalence to the stated value.